mono-shlib-cop - Online in the Cloud

PROGRAM:

NAME

mono-shlib-cop - Shared Library Usage Checker

SYNOPSIS

mono-shlib-cop [OPTIONS]* [ASSEMBLY-FILE-NAME]*

OPTIONS

-p, --prefixes=PREFIX
Mono installation prefixes. This is to find $prefix/etc/mono/config. The default
is based upon the location of mscorlib.dll, and is normally correct.

DESCRIPTION

mono-shlib-cop is a tool that inspects a managed assembly looking for erroneous or
suspecious usage of shared libraries.

The tool takes one or more assembly filenames, and inspects each assembly specified.

The errors checked for include:

* Does the shared library exist?

* Does the requested symbol exist within the shared library?

The warnings checked for include:

* Is the target shared library a versioned library? (Relevant only on Unix systems,
not Mac OS X or Windows.)

In general, only versioned libraries such as libc.so.6 are present on the user's machine,
and efforts to load libc.so will result in a System.DllNotFoundException. There are three
solutions to this:

1. Require that the user install any -devel packages which provide the unversioned
library. This usually requires that the user install a large number of additional
packages, complicating the installation process.

2. Use a fully versioned name in your DllImport statements. This requires editing
your source code and recompiling whenever you need to target a different version of
the shared library.

3. Provide an assembly.config file which contains <dllmap/> elements to remap the
shared library name used by your assembly to the actual versioned shared library
present on the users system. Mono provides a number of pre-existing <dllmap/>
entries, including ones for libc.so and libX11.so.

EXAMPLE

The following code contains examples of the above errors and warnings:
using System.Runtime.InteropServices; // for DllImport
class Demo {
[DllImport ("bad-library-name")]
private static extern void BadLibraryName ();

[DllImport ("libc.so")]
private static extern void BadSymbolName ();

[DllImport ("libcap.so")]
private static extern int cap_clear (IntPtr cap_p);
}

Bad library name
Assuming that the library bad-library-name doesn't exist on your machine,
Demo.BadLibraryName will generate an error, as it requires a shared library which
cannot be loaded. This may be ignorable; see BUGS

Bad symbol name
Demo.BadSymbolName will generate an error, as libc.so (remapped to libc.so.6 by
mono's $prefix/etc/mono/config file) doesn't contain the function BadSymbolName

Unversioned library dependency
Assuming you have the file libcap.so , Demo.cap_clear will generate a warning
because, while libcap.so could be loaded, libcap.so might not exist on the users
machine (on FC2, /lib/libcap.so is provided by libcap-devel , and you can't assume
that end users will have any -devel packages installed).

FIXING CODE

The fix depends on the warning or error:

Bad library names
Use a valid library name in the DllImport attribute, or provide a <dllmap/> entry
to map your existing library name to a valid library name.

Bad symbol names
Reference a symbol that actually exists in the target library.

Unversioned library dependency
Provide a <dllmap/> entry to reference a properly versioned library, or ignore the
warning (see BUGS ).

DLLMAP ENTRIES

Mono looks for an ASSEMBLY-NAME mapping information. For example, with mcs.exe , Mono
would read mcs.exe.config , and for Mono.Posix.dll , Mono would read Mono.Posix.dll.config

The .config file is an XML document containing a top-level <configuration/> section with
nested <dllmap/> entries, which contains dll and target attributes. The dll attribute
should contain the same string used in your DllImport attribute value, and the target
attribute specifies which shared library mono should actually load at runtime.

A sample .config file is:
<configuration>
<dllmap dll="gtkembedmoz" target="libgtkembedmoz.so" />
</configuration>

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